What are examples of commensalism in deciduous forests?

First, to get everyone up to date, you are referring to Ecology and the relationships between organisms. Mutalism, for example is a relationship in which both organisms get something; Parasitism is where one organism benefits while the other is harmed, and Commensalism is a relationship in which only one of the organisms benefits while the other receives no benefit AND no harm.

Deciduous trees are ones that lose its leaves, usually seasonally.

The most common example of a Commensalistic relationship in this type of forest would be algae or moss. They grow on tree bark and have no affect on the tree itself. Another example would be animals that make homes out of trees without damaging them. Of course, some do, but the ones who do not are in a Commensalistic relationship.